Botulism risk through salted and dried roach
The roach, which is widespread throughout Europe and which also lives in the brackish water of the Baltic Sea, can contain the bacterium Clostridium (C.) botulinum and botulinum neurotoxins without the fish being recognisably spoiled. "That's why there is a risk that consumers who eat salted and dried roach which has not been sufficiently heated could contract botulism," explains BfR President Professor Dr. Dr. Andreas Hensel. The risk increases if the fish have not been carefully gutted and roach offal is also consumed. For this reason, the BfR recommends to gut roach carefully and completely soon after the catch followed by thorough rinsing on the inside and outside. In addition to this, roach should be stored at a maximum temperature of 3 °C prior to salting, additionally cooled during salting for several days and sufficiently salted when drying above 8 °C. The BfR recommends that consumers only eat salted and dried roach that have been sufficiently heated for at least ten minutes with a core temperature of 85 °C or above.
Botulism is a serious disease caused by botulinum neurotoxins. These toxins are mainly formed by bacteria of the species C. botulinum which can only propagate in the absence of oxygen. The bacteria are capable of forming heat-stable spores which are extremely resistant and which can also survive unfavourable environmental conditions. The bacterium occurs all over the world in soil and coastal waters, where it can also be ingested by roach. The propagation of the bacteria and formation of neurotoxins can be stopped by proper salting and drying of the fish, thus significantly reducing the water content. The disease begins with non-specific symptoms, such as nausea, vomiting and gastrointestinal disorders, but usually leads to specific neurological disorders, such as impaired vision, dry mouth, speech and swallowing difficulties which can be fatal in extreme cases. It cannot be transferred from humans to humans.
Several cases of botulism in humans were reported in Germany and Spain at the end of 2016 which were traced back to the consumption of salted and dried roach. Once the botulism cases were recognised, the suspect goods were recalled from the supplied companies, and in the affected countries public warnings were issued against the consumption of these goods.
The BfR has no information on the production and treatment of the recalled batches, nor does it have any data on the frequency of consumption of these fish products. Furthermore, the information on the recalled batches provided in the European Rapid Alert System for Food and Feed (RASFF) shows that the sources, as well as the production and packaging methods, best-before dates and required storage temperatures of salted and dried roach, are different. Nevertheless, in order to estimate the occurrence and behaviour of C. botulinum in salted and dried roach, the BfR conducted literature studies and made estimates on the basis of existing mathematical models.
The BfR advises consumers only to eat salted and dried roach that has been heated to a core temperature of 85 °C or more for at least ten minutes. The offal of insufficiently heated roach should not be eaten either.
About the BfR
The German Federal Institute for Risk Assessment (BfR) is a scientifically independent institution within the portfolio of the Federal Ministry of Food and Agriculture (BMEL) in Germany. It advises the Federal Government and Federal Laender on questions of food, chemical and product safety. The BfR conducts its own research on topics that are closely linked to its assessment tasks.
The BfR is celebrating its 15th anniversary this year. To mark the occasion, the institute has published a jubilee brochure (in German) which can be downloaded or ordered free of charge at http://www.bfr.bund.de/en/publication/brochures-61045.html.
This text version is a translation of the original German text which is the only legally binding version.